Name
Class
Relationships Among Elements
Date
Background Information
The periodic table is a wonderful source of information about all of the elements scientists have
discovered. In this activity you will investigate the relationship among the elements’ atomic radii, and the
positions in the periodic table.
The atomic radius is the distance from the nucleus of an atom to the outermost electron. This is
basically how big the atom is.
The radii for elements with atomic numbers from 3 – 38 are given in table 7-1. The radii are so small
that a very small metric unit called a picometer is used. A picometer (pm) is one trillionth of a meter.
Objectives
In this experiment you will:
 Plot the atomic radii of elements with the atomic numbers 3 – 38 and
 Examine the graph for repeated patterns
 Interpret your graph results to determine relationships among various elements
Equipment
 Copy of the periodic table
 Graph paper
 pencil
Data Table
Name
Symbol
Aluminum
Argon
Arsenic
Beryllium
Boron
Bromine
Calcium
Carbon
Chlorine
Chromium
Cobalt
Copper
Fluorine
Gallium
Germanium
Iron
Krypton
Lithium
Al
Ar
As
Be
B
Br
Ca
C
Cl
Cr
Co
Cu
F
Ga
Ge
Fe
Kr
Li
Atomic Atomic
Number Raduis
(picometers)
13
143
18
191
33
121
4
112
5
85
35
117
20
197
6
77
17
91
24
128
27
125
29
128
9
69
31
134
32
123
26
126
36
201
3
156
Name
Symbol
Magnesium
Manganese
Neon
Nickel
Nitrogen
Oxygen
Phosphorous
Potassium
Rubidium
Scandium
Selenium
Silicon
Sodium
Strontium
Sulfur
Titanium
Vanadium
Zinc
Mg
Mn
Ne
Ni
N
O
P
K
Rb
Sc
Se
Si
Na
Sr
S
Ti
V
Zn
Atomic Atomic
Number Raduis
(picometers)
12
160
25
127
10
131
28
124
7
71
8
60
15
109
19
231
37
248
21
162
34
119
14
118
11
186
38
215
16
103
22
147
23
134
30
134
Conclusion Questions
1. Look at the shape of your graph. What pattern do you observe?
2. What family is represented by the high peaks in your graph?
3. What family is represented by the low peaks in your graph?
4. What family is represented by the smaller peaks just before the high peaks in your graph?
5. What do you notice about the radii of the elements at the high peaks as you move from left to right?
Look at your periodic table and find the element that represents each high peak. What does each high
peak begin in the periodic table?
6. What happens to the radii of the elements between the two highest peaks? What does each of these
groups of elements represent?
7. How can a graph such as the one you made help to predict the properties of elements that have not
yet been discovered?
8. How do the radii of the metals in each period compare with the radii of the nonmetals in that period?